Telephone system



July 19, 1932. A. WASCHNACK TELEPHONE SYSTEM Filed Sept. 12, 1951 3 Sheets-Sheet 1 5:11:11 Nasal-mack July 19, 1932. A. WASCHNACK TELEPHONE SYSTEM 5 Shets-Sheet 2 Filed Sept. 12. 1931 Inuen :11- Hdmlf [r-Jaazhnack July 19, 1932- A. wAscHNAcK TELEPHONE SYSTEM Filed Sept. 12. 1931 5 Sheets-Sheet 3 RNA limit L7 Hdnlf waschnack Patented July 19, 1932 UNITED STATES PATENT Q'FFLCE.

ADOLI'? WASGHQTACIL- OF NEU-FINKENKRUG, NEA R BERLIN, GERMANY, ASSIGNOR 110 SIEMENS & GERMANY Application filed 1September 12, .1931, Serial calling an operator of his own .exchange, re-

10 questing this operator to set up a new connecting route to the second speaking station. These arrangements have .the disadyantage that the switching over of the connection cannot take place with the required speed when {1 theoperator isbusy setting up other connections. On the other hand, these arrangements require comparatively complicated devices which, particularly in small systems, have to be considered for the sakeof economy. The object of the present invention isto set up connections with greater speed and using a small a number of .auxiliarydevices as possible, thisbeing. achieved by switching means being provided which, under .the influence of a special switchingbperation at the speaking station calling a second subscriber of its own exchange, cause'the switching over of the connection to the calledsecond subscriber.

The arrangement according to the invention offers important advantages particularly in cases concerning exchanges which periodically lack the services of an operator for example, at night, or: the operator being busy setting up other connections. nag .alsorof advantage in substation systems where change lines are switchedthrough to certain speaking stations associated with/the subon system at certain periods or: in cases where the services ofa special operator isnot available such as for example, a speaking station associated with a substation system in which all incoming-exchange ealls al e received and switched over to the required subscriber. i

in the first mentioned case various devices have-been suggested in which,=for errample a small auxiliary exchange is installed atthe stations to which incoming unction lines are switched through at certain periods (at natsxn axrrnnensnnnsonarir, on srnivinnss'rlin'r nnan BERLIN,

TELEPHONE s sTEM -team an in ust i Augus a 1930.

night) and over which only preferred 'X- changes 'canbe reached. It fiso nlyto be: X- pe'cte'd these devicesdsim'l suggested for automatic systems socalled {toll control positions are cemparatiuely coin licated and in additio completelyjpreve ita certain'numberofspeaking station's om ejc eivin g any incoming connections. Alhth'ese disadvantages areejliminated by the pr e 'j invention.

According to one vfeature of theinvent ion, part of the connecti g dQiZices of hangs which are used for speaking c0 J a loc l ca l a e ed i the se t .zr te an part in thespeaking routei heica'se ofc'alls 9 incoming from anotherexchange. I i According to another featureiof the invention, in thejsetting upof fa conneetion to another exchange, aline outgoing intliji'sdirejc- .tioni's connected in thecalling exchange we line whichis utilized to setup inte' rial 'QQfi- 'nections. v r s A still further feature ofthe invention re l ws o t phe ystemfha insi li t ity of exchanges in Whichthe @u amvin l r m o he ei chense far r edfby' f'spee ing' station and transferred (to the required speaking station. This accomplishedby the speaking station which freceiifesflthejcalls from other exchanges bringing @bOLlQtheset- 8O ting of the connecting devicefAS) u's'eld for itsconnection o the callingline, t

quiredispeakingst-ation. Referring now to thedrawings comprising Figs. 144 ,they show bynieajns'iof the lfl'sll'al .85 circuit diagrams a sutficien'tam untof a paratus in atelephone system embodying 't e featureslot the invention to enable the a "l to b'e und erstood. v l Figilfshows a sub-exchange comprisinga call finder AS arranged to ifin'ctthei callinjg subsc'ribers 'line a'nd a finla'l selector LW over which .local' connections are established. 'Trunlrconnections to another exchangeare made over trunk lineZA. p9 -Fig. 2 shows a modification ofl the system, shown; in;;Fig.31;fin that, the outgoing connect im m mad v w t hes.Qfa ant matic' p va Q hz geWh Q n oming eoane tion .are set up by an operator .4

Fig. 8 shows a modified circuit for the release relay N.

Fig. 4 shows a modification of the portion of the circuit of Fig. 2, which controls the setting up of inquiry connections.

1. Setting up an internal connection If, for example, subscriber N1 wishes to set up a connection with any subscriberof his own exchange, the following circuit is set up when he lifts his receiver: earth, contact 1t over the subscribers line loop, resistance VVZ'Z, contact 2t, c-wiper of the final selector LVV in zero position, winding I of relay V battery, earth. Relay V is energized in this circuit and by the closing of contact 3 effects the connecting up of the rotary magnet DAS'ofthe call'finder AS over: earth, relay interrupter RU, contacts 252%, 3 1), 53, rotary magnet DAS, battery, earth. The call finder AS is advanced by means of the rotary magnet until the following circuit for winding I of relay S has been set up: earth, contact 1t over subscribers line loop, b-wiper of the'call finder AS, contacts 6t, 71, winding I of relay S, battery, earth. By means of relay S, now

energized, the rotary magnet DAS of thecall finder AS is brought to rest by opening con tact 55. By the closing of contact 83 the relays T1 to T4 are energized over: earth, contact 88, relays T1 toTa, battery, earth. Relays T1 to T4 actuate all the t-contacts whereby thecalling circuits (circuit of relay V) of all the subscribers, for example, subscribers N, N1, N2 are broken at contacts 1t, 2t,'9t and 10t. The device for all the other subscribers is hereby guarded.

Upon the energization of relays T1 to T4 the relay V is energized over: 'earth,.winding III of relay S, contact 17t, c-wiper of the final selector LIV in zero position, winding I of relay V, battery, earth.

The feeding circuit for the calling subscriber Nlnow extends over: earth, contact 11t, winding II of relay S, contact 121 winding II of relay X, a-wiper of the call finder AS to subscriber N1, b-wiper of the call finder AS, winding I of relay X, contact 71', winding I of relay S, battery, earth.

The subscriber now sends out the impulses for the setting of the final selector LVVQ'. Ac-

cording to these impulses relay S is disconnected from battery and actuates the rotary magnet DLW of the final selector in the following circuit: earth, contacts 137%. l ft,

15s,'wind .ing II of relay V, contactlfia, rotary magnet DLWV of the final selector LW, battery, earth. The final selector LlVis now set tothe required contact. Relay V remains energized in the circuit for the rotary magnet only during the impulse series but releases after this impulse series, as the circuit for winding I of relay V is broken by the advance of the switch wiper 0 associatedwith the final circuit.

selector LW. Therequiredsubscriberiscalled in the following circuit: earth contact 11t, winding II of relay S, contact 121", winding II of relay X, contact 1839, a-wiper of the final selector LW to required subscriber, bwiper of the final selector Ll/V, contact 19a, winding I of relay U, contact 20 0 over the contact which closes every four seconds, ringing current source of supply RQ.

When the required subscriber answers, the relay U is connected to battery over the foursecond contact being set in its normal posi tion and resistance VV2'3. By the opening of contact 19%, effected by relayv U,'as well as bythe closing of contact 21a the speaking leads are connected up and the ringing current is broken. Relay U remains energized contact 23a, contact'24w, rotary magnet DLW of the final selector LlV, battery, earth. The rotary magnet DLl/V does not operate in this The speaking connection between the calling and the required'subscriber is thus set up.

The established connection is released in the following manner: If either the calling or the called party replaces the receivers, re

lay S is disconnected from the battery and by the opening of contact 88 causes the release of relays T1 to T 1. Hereby all the t-contacts arerestored to their normal positions. By the closing of contact 2525 the following circuit for the rotary magnet DLW of the final selector is set. up: earth, relay inter; rupter RU, Contact 2517', c-wiper of the final selector LW in position 1--10, rotary mag net DLlV of the final selector, battery, earth. The rotary magnet DLl/V operates until the final selector LVV has reached its zero position and thereby broken the above described circuit. is broken at contact 22t. All the'switching means are now restored to'normal and the.

device can be used for a fresh connection. 2. Setting up an ewchang connection If, for example, subscriber N1 wishes to set up a connection with the exchange, the.

setting of the call finder AS to the calling The locking circuit for relay U subscriber is effected in the same manner as 7 described in the above. When the call finder has been set as required, the subscriber N1 momentarily presses key T whereby the differential relay X in the feeding circuit is enits contact 8079 as follows: earth, contacts 26t, 271", 29m, 3070, winding I of relay'H, battery, earth. Relay H is a two step relay energized in the first and second stage in the last described circuit.

finder AS and final selector LIV to the exchange lead 2A is effected byarelay P opening-the'contacts 34p and 18p and closing contacts 35p and 36p. The exchange is called by the operation of relay H.

After the setting of the call finder AS the relay S, as already described, is energized, and relays X, P and H likewise energize by themomentary depression of the key T1; By

the operation of relays 'S and 'H, a bridge is set up between the exchange line over contacts 378, 38k, and relay Digsaid bridge causing relay Dr in addition to the call finder in the exchange to be energized. The exchange :line'is switched through at contacts 39d?" and 40d? by this relay Dr.

The setting of the switches in the exchange is efiected-in known manner'by the feeding bridge relay S, in which case the contact 378 is the impulse contact. After the switches in the exchangehave been properly set the two subscribers can converse with each other.

3. Setting up 0 7 an enquiry connection during an exchange comiersatw'n If the subscriber wishes to speak to another subscriber associated with a sub-exchange during the exchange conversation, he againpresses momentarilythe key T1, thereby energizing thedifi'erential relay X. By the opening of contact- 3350 and the closing of contact 29512, the winding Iof relay P and winding II of relay H are short-circuited. Relay P releases and opens at contact 30 the locking circuit for relay H overwinding II of relay H. This relay H is maintained energized over: earth, contact 262?, resistance Wi l, contacti'z and-II, winding I of relay H, battery, earth, but when energized in the above circuit actuates only the contacts in the first state, thatis to say those of the h-contacts denoted by I or I andII, respectively.

-By the opening of contacts-35p'and 36p and the-closing of contacts 18;) and 3479, the calling subscriberis switched over to'the line leading to'the final-selector'LW and can, therefore, asalready described, set up a connection with-any subscriber associated with the substation. During the enquiry connec -tion the lockingbridge between the exchange "line is maintained over contacts 378, 38k, choke Dr.

If the calling-subscriber Nl after the enqu-iry .connection'fhas been effected 'wishes ito use the exchange :hne again, the switching over is effected in the following manner. Re-

lay X is re-energized by a momentary pressing of the key and connects up winding II of relay Ploy-"the,cl'osingiof contact 2951:. Relay P, as already described, is connected up to theexchange line and energizes .relay Hlin the second stage. The rotary magnet DLWV of the final selector LW receives impulses frmn therelay interrupter RU over: earth, relay interrupter, contacts 56%, 57h ,d-wiper ofthe final selector in position 1.10, rotary magnet DL'l/V, battery, .earth, until the-final selector LW has reached its zero position and thereby broken the vlastdescribed circuit.

If, on the-other hand, subscriber N1 would wish to hand over the exchange connection to the subscriber with whom he has had'an enquiry connection, the subscriber N1 must press the key T1 a longer periodthan heretofore. Relay X is thereby energized accordingly, with the consequence that the thermo I relay TH is energized over contact 4100, thereby causing contact 422% to close. A. circuit for relay R- is set up over: earth, contacts 41%, 42th, relay R battery, earth. By the closing of contact 431", after relay S has released by the opening of contacts 121" and 7 r,

the relay R is maintained energized over: earth, contacts 4A6, 437", 158, relay R, battery, earth. The relays T1 to T4 are maintained energized iover contact 49r-at the release of relay S which causes contact 88 to be opened,

the exchange connection ibeing maintained independent of contacts 378 over contact 53h. The following circuit for'the rotary magnet DAS of the call finder'is set up at contact 4L6rz-earth, relay interrupter RU,

contacts 461", 58, rotary magnet DAS' of call finder AS, battery, earth. The rotarygmagnet DAS actuates the call finder AS,until 'the following circuit for relay S'has been established over winding I: earth, battery,

winding I of relay S, contact 471", c-wiper of the call finder AS in the position of the en- -quiry subscriber (for example 3), c-wiper of the final selector LW, likewise in the position of the enquiry subscriber 3, over line 48, contact 172$, winding III of relay S, earth. The

circuit for the rotary magnet DAS of the call finder AS is broken by the opening of contact 58. The call finder is thus set to the subscriber with whom the subscriber N1 has.

had an enquiry connection. By the closing of contact 548, relay P is energized over: earth, contacts 26t, 281, 54s, 33%, 3279, winding II of relay P, battery, earth. The switching over to the exchange line at contacts 35p and 36p now takes place while relay H is energized in the second stage bythe closing of contact 30;). A locking circuit for relays-P and'H isset up over contact 31h when relay R releasesjafter the openingof the 'circuit'for this'relay R at contact 458.

The locking circuit for relays P and H then extends over: earth,.contacts 26a, 277", Winding II of relay H, winding I of relay P contacts 81h, 30p, winding I of relay I-I, battery earth. If the subscriber with whom an enquiry connection has been set up is switched over to the exchange line, the release of the final selector is effected in thc following manner: On the energization of relay P, the relay H is energized in the second stage as already mentioned. When the final selector is properly set, the rotary magnet DLW is actuated until the final selector has reached its zero position over the following circuit: earth, relay interrupter ItU, contacts 56ft and 57h, cZ-wiper of the final selector in position 110, rotary magnet, battery,earth.

4. Incoming ewchomge connections.

If a call arrives from the exchange, the call ing device AZ, for example, a bell, is oper ated in the usual nianner'by the ringing current issued from the exchange. This c ll ng device AZ is located in the subscribe room which is provided for the connections causesthe energization of relay? over con tacts 26t 277 2900 32 .with the requests of the cal.

, 10, winding II of relay P, battery, earth. Relay P effects the switching over to the exchange line and the speak-- ing station N is nowin a position to comply ng enchange subscrib'er. The conversation ah the required subscriber is initiated in the following method and manner:

hen the speaking station N has come into communication with the required subscriber, the key T is again depressed, whereby the switching over from the exchange line to the wfinal selector IIW is effected in the already described manner. The final selector LI 7 is set to the required subscriber by the speaking station N. When the called'subscriber answers and is advised by the speaking station N that he is required by the exchange, the key T at the speaking station N maintained depressed a somewhat longerperiodwhich causes that the call finder AS, over which the speaking station N receiving the exchange connections was connected to the calling exgization of relay S, relay P is energized which causes the switching over to the exchange line at contacts 18p and 84; The individual selector LW is utilized as a settin route while the spea ring route for the exchange connection extends over the call finder AS.

Subscribers entitled to various degrees of preference can be accommodated in the system. Thesetting up of an exchange connection for subscribers not entitled thereto is prevented in each case. The setting up of an exchange connection in an outgoing direction is prevented by the subscriber,.for example N2, who is not entitled to connections with the subscribers associated with the exchange not being provided with an earthing key. He is therefore unable to effect the switching-over to the exchangeline. I

In the case of incoming calls,.the setting up of an exchange connection to asubscriber not entitled thereto is prevented by the test circuit of relay S not being established over the c-wiper of the call finder AS and the final selector LIN after the subscriber has been marked by the setting of the final selector Iii V and the call finder AS to the denoted subscriber (by keeping the key T depressed a longer period), as the connection between the contacts of the 0-Wipers of the call finder AS and the final selector IN? is broken'for subscrib rs not entitled hereto at the connecting station /51. An enquiry connection during an exchange conversationby the speaking station N or another station entitied to exchange connections setting up connections with a subscriber not entitled to exchange connections is, however, possible as shown in the above, a connection with the subscriber. not entitled to exchange connections being set up over the inal selector IivV.

If a call is received whilea conversation is being hel'c, the speaking station N is in the device at the speaking station N and further connects up the induction winding J of a signalling device-to the winding S3 by closing contact 52612. Hereby a signal is inductively transmitted over the feeding bridge,

and also a speaking subscriber who, in the same manner as already described in the case of the subscriber N, receives an incoming exchange call after the switching over tothe exchange line and then switches him over to another subscriber.

In Fig. 2 a sub-exchange device is shown with its main parts the outgoing exchange trafl'ic being efiected over the switches of an automatic private exchange while incoming connections are set up by meansof plugs and acks to the individual substations. The devices necessary for the enquiry of the incoming exchange calls have been omitted as they are not necessary for the understand ing of the invention and it will be assumed that the operators position is vacant (for example during the night) in which case the plug St has been inserted in the ordinary jack 2 connecting up a substation N3 which is to set up the incoming exchange connections during the absence of the operator.

The operation of the circuit will now be described in the case of incoming exchange calls.

The alternating ringing current transmitted by the exchange periodicall energizes the line relay A. By means of 1 s contact 6045 this connects up a ringing relay R which, by throwing over contacts 617" and 621" transmits the ringing current to a substation connected to the jack K2 into which the plug St has been inserted. In the substation N3 the test relay P has been connected to battery by the insertion of the plug S25 and this relay, by means of its contacts 63p and 64p switches through the speaking leads to the The subscriber N3 is guarded in substation. known manner by the short-circuiting of winding II of relay P at the contact 65p.

As soon as the plug is inserted into the jack relay P is immediately energized in the shown embodiment. It is, however, possible to make the test relay P effect the switching over of an exchange connection only when such a connection is required, with the consequence that the subscriber N3 will be engaged only when such a call arrives. By the throwing over of contacts 611 and 621" the ringing current will be sent out to the substation N3. If this subscriber lifts his receiver in a ringing pause, relay S is energized, whereas relay X, located in series with relay S, will not be energized as its two windings are differentially connected. A loop to the exchange is formed by means of contact 668 and this loop completes a circuit for the ringing current from the exchange and substation at contacts 6801 and 69c1. The substation N3 enquires the number wanted by the calling subscriber. In

case the calling subscriber wishes to speak,

to another substation, the substation N3 presses its earthing key momentarily whereby the differential relay X is energized over the winding II to which battery is applied, and by means of its contact 7000 energizes relay D which with its contact 71d prepares a locking circuit for itself and also by means of contact 7203 prepares the circuit for relay U. When the earthing key is released, relay contact Ma and the choke D12 while con tacts 7 5a and 76a connect the section of the exchange line which is associated with the substation to an enquiry lead RA. A loop is formed over contact 668 and choke Drl which causes that the preselector or call finder'is connected up to a group selector or final seQ lector. StatiOn NS now dials the required substation and notifies the arrival of a call. If the called station does not wish to receive the call or is engaged, the-night operating station can release the enquiry connectionby a further momentary depression of the earthing key and advise the calling subcriber. accordingly. Y

When the earthing key is depressed the second time, relay X is re-energized. Contact73m breaks the circuit for relay D and winding I of relay U. Relay D releases but a fresh locking circuit for relay U is formed over its winding II and contacts 77a and 7 003.

When the earthing key is released relay U, due to the release of relay X, releases also and. the station N3 isagain connected up to the exchange subscriber. 3

If, however,-the called substation accepts the exchange call, the subscriber at, station N3 presses the earthing key a somewhat longer period (about two or three seconds). Relay X is thus energized during a longer period which causes a thermo relay 'Ih to be heated over: earth,vcontacts 70:0, 7714, thermo relay Th, battery, and closes its contact 7 8th after a certain period. Hereby a circuit fora relay N will be set up over itswinding I parallel'to the winding of the thermo relay Th, and over the closed therm o contact 78th. A connection between the exchange. line AL and the enquiry line RA is set up by the contacts 79a and 801% over two condensers and by means of contact 81% the loop to the exchange is maintained. At contact 82% winding II of relay N forms a bridge between the two lines of the enquiry leads RA which maintains the circuit for the enquiry call. By contact 8311 the test circuit for station N3 is broken over relay P which thus releases and disconnects the, exchange line at contacts 63;!) and 64;) whereby a listening in to the con.-

the exchange is opened by contact 81% and the releaseof the connection thus effected.

The manner of maintaiinng relay N in the 1 system adopted in the private installation can be efiiected in various ways. If, for ex ample, the system includes a final selector which has a common feeding for both calling and called subscribers, the circuit for relay N can be set up according to Fig. 3. The

two windings'of relay N are placed in parallel to the feeding relay of the final selector and maintained over the loops of the called subscriber. When this subscriher'has ended the conversation the circuit for relay N' is broken and the release thereby effected. I

It is assumed in the described examples that only substations entitled to exchange connections are connected up to, the automatic private installation. Should this not be the case and there are no private systems en titled to exchange connections, the connect ing up of exchange calls over enquiry lines to private systems are prevented by suitable circuit arrangements. In such cases it is recommended that the substations and private stations are split up into various 10 or 100 line groups.- If, at the setting up of an enquiry connection the number of the outgoing impulse series '18 counted by means of a small switch, the unauthorized connections can be prevented according to Fig. l in the following manner.

It will be assumed that the substations comprise the numbers 0 to and the private stations 50 to 100. It can be ascertained by means of the first impulse series whether the subscriber call-ed over the enquiry line is en titled to exchange connections or not. The

J operator at substationNffi presses his earthing key and efiects the switching-over to the enquirylconnection RA already described in con]unct1on with Fig. 2. The required subscriber is then dialled. According to Fig. 4c

. contact 848 of thebridging relay is intermittently de-energized during the impulse series and closes a circuit for the rotary magnet DM of the selector switch over: earth, contacts 848, a, thelow resistance winding I of the slow acting relay H, switch wiper a, rotary magnet DM, battery. At the first rotary step this circuit is broken by the switch wiper a, but the circuit for relay H and the rotary magnet DM is maintained over the traversed contact segment and contact 86h. After the first impulse series, the contact 848 remains open a somewhat longer period and relay l-l' releases. The rotary magnet DM can no longer be actuated by the succeeding impulse series as contact 86h is opened. If the rotary switch now has set its wiper Z) to a contact which is connected to the heating winding of the thermo contact, the switching over of the connection to the called second subscriber can only be set up by an extended depression of the key as described in the case of Fig; 2.

7 When relay U releases at the release-of the connection the rotary magnet DM is con nected to battery over: earth, contacts 87%,

8814, 89k traversed contact bank, wiper a,

rotary magnet DM,-battery. At each armature attraction the rotary magnet DM actuates contact SOdm over which relay H is energized over winding H. The circuit for the rotary magnet DM is broken by means of contact 89h, the rotary magnet DM releases and I opens its contact 90clm..

Hereby the circuit for relay H is broken etc. With the aid of re; lay H the rotary switch is thus restored to its original position.

The facility to set up an exchange connection from one substation to another without the intervention by an operator can also be effected in the case of outgoing calls as willbe seen from the following description. ln'or- I der to set up a connection with an outgoing exchange line, the subscriber dials a certain number and the final selector sets the c-lead to a free exchange line. A circuit for the final selector extends over earth, contact 9 1%, relay C of the exchange line, contact 92$, resistance, battery, earth. The connecting up of the speaking leads is effected. in the final selector in known manner and the relay allocated to the exchange line causesthe energization of relay S but not relay X. Thejslow acting relay T'is connected up by contact 930 for the purpose of initiating the release.

The first substation then dials the required exchange subscriber in the case of an automatic exchange. The same facilities as in the case of incoming calls are now provided, that is to say, over the enquiry lead RA a second substation can be called. and by a somewhat ice longer depression of the earthing key the switching'over of the exchange line to the second substation call-ed over the enquiry lead can be effected. The c-lead is broken by contact 91% for the purpose of cutting off the first connection, the final selector is released and the exchange line is simultaneously guarded for theduration of the conversation.

As will be seen from the specification, no alterations are necessary at the substation to enable this station to switch over exchange connections.

The feature of the present-invention is not limited only to the described arrangements, but can also be used in the case of engaged substation exchangeswhen the switching over signal by pressing the earthing key a longer period, in case no enquiry connection is set up, for example, a special signal can be given in this case at the exchange which demands inclusion in the exchange conversation.

What is claimed is:

1. In a telephone system, a local exchange, a trunk xtending from a main exchange to said local exchange, a finder connector link at said local exchange for establishing local connections, means for connecting the talking conductors oi said trunk to the talking conductors of said link, and means'for controlling a portion of said link as a setting route and another portion of said link as a speaking route when incoming connections are set up over said trunk by said main exchange.

2. A system as set forth in claim 1, in which the desired subscriber is denoted by the setting of the connector portion of said link and subsequently the talking connection is set up over the finder portion of said link.

3. A system as set forth in claim 1, characterized by the provision of a station at said local exchange for receiving incoming calls,

together with means at said station for controlling the setting and talking connections for said calls.

4. In a telephone system, a local exchange, a trunk extending from a main exchange to said local exchange, a common line in said 10- cal exchange which is used for setting up local connections, a station at said local exchange for receiving incoming connections from said main exchange, a switching device at said local exchange controlled by said receiving station for the setting up of incoming connections, said switching device also being controlled by other stations at said local ex change entitled to make connections to said main exchange.

5. In a telephone system, a local exchange, a trunk extending from a main exchange to said local exchange, means for establishing a connection between two subscribers one in each of said exchanges, a switching device at said local exchange, means at the local subscribers station for operating said switching device to connect the main exchange subscriber to another local subscribers station, and means for preventing the switching device from connecting up the second mentioned local subscribers station when said second station is not entitled to connections from the main exchange.

6. In a telephone system, a sub-exchange, a plurality of subscribers, a common trunk line accessible to said subscribers over a common line finder, a common connector controlled by any one of said subscribers over said line finder and common trunk to complete local connections, a trunk line to a main exchange, and a switching device controlled by any one of said subscribers to disconnect said common trunk line from said connector and to connect said common trunk line to sand main exchange trunk.

7. In a telephone system, a sub-exchange,

a plurality of subscribers, a comon trunk line accessible to said subscribers over a common line finder, a common connector controlled by any one of said subscribers over said line finder and common trunk to complete local connections, a trunk line to a main exchange, a switching device controlled by any one of said subscribers to disconnect said common trunk line from said connector and to connect said common trunk line to said main exchange trunk, and means for disconnecting said main exchange trunk from said common line and for connecting said common line to said connector to complete a connection to a local subscriber without releasing said main exchange connection.

8. In a telephone system, a local exchange, a trunk extending from a main exchange to said local exchange, a station at said local exchange for receiving incoming calls from said main exchange, a finder for connecting said station to said trunk, a called station, a connector linked to said finder and controlled from said first station to select said called station, and means controlled by the sub scriber at said first station for starting the reoperation of said finder to connect the called station to said trunk.

In Witness whereof, I hereunto subscribe my name this 19th day of August, A. D. 1931.

ADOLF WASCHNACK. 

